Recently, a website was constructed and launched by our chums in Reefnet that provides an answer. As a resident it's a rather addictive site, checking out each category to see what businesses there are, and where they are located in the archipelago.
It also gives a better impression of what goes on here. Cattle farming, for example, shows that contrary to some people's perceptions, crofting land is not just populated by sheep. Yes, we have banks and supermarkets (some tourists still think we have neither, and stock up before leaving the mainland), and the database shows which chain is (currently) predominant. There's all manner of other businesses and services, such as interior designers, opticians, and rather good dental services. And other categories, such as beauty salons, hairdressing services, health food shops, and masseuse services show that locals like to take care of themselves.
So here is the Outer Hebrides Business Directory:
...and it's fun having a good explore.
There are some gaps in the data where businesses haven't yet entered their details, for example in the vegetable growing category, or in the lack of pharmacists listed outwith of Lewis. If you run a business, want the trade and aren't included, follow the instructions on the website to get listed.
Finally - for teccies, and those into semantic web development, David Heggie the designer introduces a few additional future-proof features:
XML - listings are available in XML format - just add a ".xml" to the url - so yours is http://www.businesshebrides.co.uk/businesses/viewById/1403.xml
hCards - all listings are marked up in the trendy hCard microformat, so that your semantic-web enabled user agent can parse the address info directly from the site and do all sorts of magic with it (have a look at the site in Firefox with the Operator toolbar installed and you'll see what I mean).
You can get RSS feeds of categories. Put .RSS onto the url; e.g. http://www.businesshebrides.co.uk/businesses/browseCat/72.rss
...or locations; for example: